1. Field of the Invention
This invention relates to a process for preparing a denatured maleic anhydride-type copolymer having a controlled number of photosensitive groups, and to a photosetting polymer composition which comprises a base polymer comprising the denatured copolymer, a photopolymerizable monomer and a photopolymerization initiator.
The photosetting polymer composition is advantageously used in industries relating to circuit-printable boards and circuit-printed boards as a solder resist solder mask), a marking ink, a solder leveler ink, a material for insulation of adjoining layers of a multilayer printed board, etc.
2. Description of Prior Art
As solder resists, thermosetting solder resists such as a resist of melamine resin type and a resist of epoxy resin type have been used. Recently a UV solder resist which is curable by ultra-violet rays has found use in consumer's goods. However, for use in industrial goods, the thermosetting solder resists such as the a resist of epoxy resin type is mainly used.
In addition, various photosetting solder resists with which patternning by photolithography is possible have been proposed.
The need for high density printed circuit boards has recently grown arranged to connect IC lands. Accordingly, the solder resist must reliably cope with the requirement for manufacturing more densely arranged circuit-printed boards.
However, in the case of using the thermosetting solder resist, it is difficult to form a fine pattern because the pattern formation must be formed by a silkscreen printing process and the silk is apt to bend to lower presicion of positioning.
As for the UV solder resists, there is a problem that these show low reliability in curing a thick film, and moreover that resistance to chemicals and solvents is insufficient.
As for the photosetting solder resists, there is a problem that most of them need development using an organic solvent and such development is unfavorable in handling and apparatus.
As fluxes used for the soldering, a water soluble flux is more preferably used than a rosin type flux from the viewpoint of the simplicity of application. However, there is a problem that the known solder resists hardly have enough adhesion to the water soluble flux.